Sheridan Inc. makes unfinished bookcases that it sells for $$57.$ Production costs are $$37$ variable and $$9$ fixed. Because it has unused capacity, Sheridan is considering finishing the bookcases and selling them for $$70.$ Variable finishing costs are expected to be $$7$ per unit with no increase in fixed costs.

Prepare an analysis on a per$-$unit basis that shows whether Sheridan should sell unfinished or finished bookcases. $($If an amount reduces the net income then enter with a negative sign preceding the number, eg$.-15,000$ or parenthesis, eg$.(15,000).)$